An image forming apparatus (e.g., a printer) comprises a fixing device that causes a sheet on which an unfixed image (e.g., toner) is formed to pass through a fixing nip, and fixes the unfixed image onto the sheet by heat and pressure at the fixing nip. In recent years, fixing devices that use an induction heating method have come into practical use in recent years (note, “induction heating” means heating by electromagnetic induction herein). Such fixing devices can save more energy than fixing devices that use a halogen heater as a heat source.
As one example of fixing devices using the induction heating method, Patent Literature 1 discloses a fixing device comprising: a fixing roller composed of a core metal, an outer circumference of which is covered by an induction heating layer via a thermal insulation sponge layer; a pressurizing roller that forms a fixing nip by pressurizing the fixing roller; and a magnetic flux generator that is provided in the vicinity of the fixing roller and generates magnetic flux for causing the induction heating layer of the fixing roller to generate heat.
Patent Literature 2 discloses a fixing device comprising: a first roller; a heat generation member having an induction heating layer; a belt that is suspended by the first roller and the heat generation member in a tensioned manner due to the force of a spring; a second roller that forms a fixing nip by pressurizing the first roller via the belt; and a magnetic flux generator that (i) is positioned facing the heat generation member via the belt while maintaining a certain distance from the surface of the belt and (ii) causes the induction heating layer of the heat generation member to generate heat.